Only issue is that because of where i live i will need a permit to add walls etc, yeah i could get away with it, but the location that i really want to put it up is viewable by the road. so its sort of easier to buy one that is pre engineered for sidewalls doors etc.
And yeah i definetly thought of calling up one of those companys and having them drop off a 12x20 shed but the floor is a problem, i have engines to move around etc, they will sink into the plywood on small metal wheels and i dont really trust jackstands and a car in there. Also considered having a container dropped off for temporary and still may do that even though its illegal per town law to have one viewable by the street.
Nobody makes this stuff easy or cheap and all the laws are against you, but f em il get it done.